Generally, in most office, hospital or plant-type buildings, telephone services are provided using a conventional PABX system which comprises a PABX connected to a public switched telephone network and subscriber telephones linked to the PABX via subscriber lines. The PABX system offers certain advantages and convenience to the subscribers thereof. For instance, the use of the PABX system is inexpensive since the calls are made through wired land channels; and intra-PABX calls can be made by merely dialing subscriber numbers without pressing exchange codes.
Since, however, subscriber telephones of the PABX system are of a cord-type in most cases, a subscriber will not be able to make or take a call when he is not within immediate vicinity of his telephone; resulting in limited accessibility to the subscribers.
On the other hand, the use of digital cordless telephone system or digital cellular phone system such as personal communication services (PCS) and cordless phone 2 (CT-2) are gaining popularity in recent years; and such digital cordless telephone systems provide mobile public access to the users thereof as long as they are within the service area thereof. However, the use of digital cordless telephone systems still remains costly because the signaling within the system is carried out by radio channels through air.
Accordingly, it would be desirable to devise a system taking advantage of both the cost-effectiveness and convenience of the PABX system and the mobile public accessibility of a digital cordless telephone system.